It is known to use spindle bearings with phenolic cages for high-speed applications such as machine tools. Such spindle bearings typically have inner and outer rings, the phenolic bearing cage radially located between the inner and outer rings, and a plurality of roller elements retained by the bearing ring. In a radially outwardly guided configuration, an outer circumferential surface of the bearing cage (the land guiding surface) is engaged with and guided by an inner circumferential surface of the outer ring (land surface). Oil from bearing grease or similar lubricant forms a lubricant film between the land guiding surface and the land surface. In a radially inwardly guided configuration, an inner circumferential surface of the bearing cage (the land guiding surface) is engaged with and guided by an outer circumferential surface of the inner ring (land surface).
Oil from the bearing grease or similar lubricant forms a lubricant film between the land guiding surface and the land surface. Lubrication of the land guiding surface is critical for operation of the bearing. However, at start up, the lubricant film is not yet fully formed between the land surface and the land guiding surface and base oil has only starting to migrate to the land guiding surface. Known spindle bearings do not provide a desired level of lubrication of the land guiding surface at start up.
EP 0 695 884 B1 discloses a greased rolling bearing element with a solid lubricating coating. The description of EP 0 695 884 B1 mentions GB 826 091 A, which described cages with metallic bodies and a plastic coating of polyamide or poly tetrafluorethylene containing about 3% of MoS2 or graphite.
The description of EP 0 695 884 B1 mentions U.S. Pat. No. 3,500,525, JP-A-62 141 314 and JP-A-3 255 223, all of which disclose a coating of MoS2 for a bearing cage. However, all these references relate to bearings for use in (high) vacuum and/or at elevated temperatures (250° C. or more). Grease lubrication cannot be used in (high) vacuum and/or at elevated temperatures.
EP 0 695 884 B1 discloses use of a coating of MoS2 and poly tetrafluorethylene over a steel bearing cage.